The present disclosure generally relates to surgical instruments, and more particularly to an instrument and associated method for clamping the patella during a surgical procedure.
Surgical joint repair and replacement involving the knee includes resurfacing and preparing the posterior articular surface of the patella (knee cap) to accept a prosthetic patellar implant. FIG. 1 shows the typical anatomy of a knee. In some cases, resurfacing of this bone is accomplished by milling or planing the surface of the patella using a powered reamer having cutting teeth. During the surgical procedure, the patella is everted involving rotating and inverting the patella by approximately 45-180 degrees to gain access to the posterior surface for reaming and resurfacing.
A patellar clamp is used to hold the patella in the everted position for reaming. The anterior and posterior surfaces of the patella are clamped between a lower fixed platform and an upper adjustable reamer guide which can be varied in distance from the platform to accommodate the thickness of the patella. The reamer guide is generally tubular shaped and functions to rotatably confine the reamer therein during the milling/planing procedure. For stable support of the reamer guide and patella during reaming, the bottom annular edge of the guide generally includes sharp and pointed teeth for gripping the posterior articular surface of the patella to be resurfaced. The teeth also resist twisting of the patella during reaming.
The foregoing arrangement, however, restricts the amount of patellar surface area that is available for reaming which is not occupied by engagement with the bottom edge of the guide and teeth. Sufficient purchase should be available on the patella to engage the guide teeth for reaming stability, resulting in the use of a reamer guide smaller in diameter than ideal and thereby further restricting the surface area of the patella available for reaming. This may result in un-resurfaced bone around the periphery of the patella. Often, the surgeon must therefore reposition the reamer clamp and reamer to access the outer regions of the patella posterior articular surface. This causes the teeth on the reamer guide to sometimes engage portions of the quadriceps and patellar tendons when clamped to the patella, which causes trauma to the tendons.